The operation of electrical transformers generates a flow in its nucleus, and an effect called magnetostriction that produces a deformation in the plates that conform it, causing vibrations that are transmitted through the oil until becoming a noise similar to a buzz, which can be annoying, depending on the area where the transformer is located.
Due to the fast growing of the urban sprawls, it is increasingly common to have to install electrical transformers near residential areas, causing an increase in noise pollution of the environment.
Over the years various solutions have been developed, focused on attacking the generation, transmission and emission of vibrations, to reduce the noise caused by the operation of electrical transformers in order to place them in locations near population centers. When total noise requirement is 20 dB or more under NEMA, solutions like decrease the magnetic flux density or use a core material of very low permeability have been proposed. Said solutions, besides been very costly, are not sufficient to achieve such noise reduction.
In view of this, the use of acoustic enclosures partially or completely covering the transformer has been proposed. U.S. Pat. No. 3,077,946, discloses examples of this type of systems, said document discloses an electric power transformer comprising a tank rigidly mounted on a basis having a nucleus, windings, an isolator, means for cooling, and an outer coating comprising at least a plate acting as a sound reflector means with flexible support means affixed to said tank and said outer coating; however, such coating hampers tank inspection and significantly increases the footprint area thereof, thus increasing difficulties for loading and moving the proposed transformer, and also preventing communication between the transformer external accessories (such as cabinets, valves, etc.) and the internal body.
Patent EP0048990 (B1) protects a noise-reducing housing for a static induction apparatus, comprising a container for holding the main body of the static induction apparatus, a plurality of support reinforcing elements attached to a side plate of the body, and means for noise reduction supported between the support reinforcing elements and the main body, including a noise insulation panel; however, once installed the means for noise reduction, is very difficult to remove them to carry out inspection operations and maintenance of equipment. Besides this, since these noise reduction means do not have acoustic sound-absorber material, the effectiveness of sound reduction obtained is severely diminished.
Patent EP0087121 (B1) protects a mechanical system that allows to decrease noise caused by operation of transformers and reactors, consisting of insulating panels having windows formed by reinforcing channels in the form of a lattice surrounding the outer periphery of the equipment housing. In this system, each sound panel substantially covers the respective window, and is supported on an elastic structure. The disadvantage of such mechanical system is that the design of panels does not coexist with the accessory outlet, so that the channel-type reinforcements continue to transmit vibrations to the panel itself, and in absence of an acoustic sound-absorber material, its efficiency is importantly reduced.
Finally, utility model CN201478084 (U) discloses a noise-reduction device for a dry reactor, comprising an upper frame, a lower frame, and a dry coil located between the upper frame and the lower frame. Said noise-reduction device comprises a structure consisting of a pair of curved panels placed in the outer side of a reactor. Said panels have inside a honeycomb structure filled with an insulating material that allows to absorb the vibrations of the reactor body. However, due to its size and design, the removal of one or all the panels of said noise-reduction device, whether for inspection or relocation of the unit, is costly. Also, the proposed design does not coexist with accessories like cabinets, switchers, electric boxes, valves, and on the tank lid there is a range of elements causing interference when wanting to implement this solution.
Systems described above also have the inherent disadvantage of requiring complicated attaching systems, which in many cases are integrally formed with the transformer body. Also, systems described above require a complete disassembly of the reactor or transformer to allow the exchange of noise-suppression systems in case of wear or failure.
In view of the above problems, there is a need to provide an easy-to-install, and also removable acoustic panel to efficiently reduce the acoustic pollution caused by operational noise of the transformer.